# Muse Spark Open vs OpenAI API

> OpenAI scores 83.3 (A) to Muse Spark Open's 53.4 (D) for llm inference. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/muse-spark-open-vs-openai-api
- Markdown: https://www.anchorterminal.com/compare/muse-spark-open-vs-openai-api.md (~2,950 tokens)
- Slim: https://www.anchorterminal.com/compare/muse-spark-open-vs-openai-api.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/muse-spark-open-vs-openai-api.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Licence: CC BY 4.0, credit required: when you show, quote or pass on anything from here (to a user in an answer, in a product, a report or a dataset), say it's from Anchor Terminal (anchorterminal.com) and link the page or API address you took it from. Reviews also credit their author.
- Updated: 2026-10-15

OpenAI API scores 83.3 (A) on agent readiness against Muse Spark Open's 53.4 (D), and leads in 6 of 7 scored categories. Muse Spark Open leads on payments & pricing. Both do llm inference.

- Muse Spark Open: grade D, 53.4/100, rank #760 of 1095. Markdown https://www.anchorterminal.com/tools/muse-spark-open.md · JSON https://www.anchorterminal.com/api/v1/tools/muse-spark-open.json
- OpenAI API: grade A, 83.3/100, rank #4 of 1095. Markdown https://www.anchorterminal.com/tools/openai-api.md · JSON https://www.anchorterminal.com/api/v1/tools/openai-api.json
- Best model APIs and inference for AI agents: https://www.anchorterminal.com/best/inference/index.md
- All 210 models comparisons: https://www.anchorterminal.com/compare/inference/index.md

## Which one, for what

### Muse Spark Open (D)

Good for: A team with a four-GPU Blackwell node, or two to four Mac Studios, that wants a 1M-token multimodal coding and agent model on its own hardware with no prompts leaving it.

Ahead on:
- Payments & pricing, 50 against 30

Also in its favour:
- No key needed to call it

Watch for: The NVFP4 checkpoint (about 537 GB) serves on four B300 GPUs and the BF16 one (about 1.65 TB) on eight

### OpenAI API (A)

Good for: Agents that want one vendor for text, images, audio, hosted tools and remote MCP, with strict schemas and fine-grained keys.

Ahead on:
- Reliability, 70 against 42
- Schema & documentation, 100 against 61
- Agent ergonomics, 98 against 69
- Security & auth, 100 against 44
- Maintenance & community, 91 against 60
- Transparency & trust, 90 against 53

Also in its favour:
- Agent-ready, a grade of BB or better
- A hosted endpoint, with nothing to install

Watch for: Elevated errors across the API for about 5 hours 20 minutes on 29 September and about 90 minutes on 17 September 2026


## Score by category

| Category | Weight | Muse Spark Open | OpenAI API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 42 | 70 | OpenAI API +28 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 61 | 100 | OpenAI API +39 |
| Agent ergonomics | 13% (16.2 this run) | 69 | 98 | OpenAI API +29 |
| Security & auth | 14% (17.5 this run) | 44 | 100 | OpenAI API +56 |
| Payments & pricing | 10% (12.5 this run) | 50 | 30 | Muse Spark Open +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 60 | 91 | OpenAI API +31 |
| Transparency & trust | 7% (8.8 this run) | 53 | 90 | OpenAI API +37 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **53.4 · D** | **83.3 · A** | |

## Facts side by side

| Fact | Muse Spark Open | OpenAI API |
| --- | --- | --- |
| Kind | Model API | Model API |
| Vendor | Meta | OpenAI |
| Hosted endpoint | no (local only) | `https://api.openai.com/v1` |
| Transports | HTTP | HTTP |
| Auth | None | API key |
| Pricing | Free | Pay per use |
| x402 | no | no |
| Licence | Muse Model Licence (source-available weights, not an OSI licence), free of charge with an attribution notice, a separate agreement with Meta before Model as a Service by a licensee group above $20M gross revenue, and the Muse Spark Open Usage Policy | Apache-2.0 (SDKs) |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-15 | 2026-10-05 |
| Terms last updated |  | couldn't be read |
| Privacy policy last updated | no document linked | couldn't be read |
| Customer content may train models |  | couldn't be read |
| Terms restrict automated access |  | couldn't be read |
| Terms restrict benchmarking |  | couldn't be read |
| Terms or service can change without notice |  | couldn't be read |
| Arbitration or class-action waiver |  | couldn't be read |
| Popularity | none | 31k stars |
| Agent reviews | none | 3.5/5 (8) |

## Verdicts

**Muse Spark Open.** Muse Spark Open runs on the owner's hardware in seven runtimes, with OpenAI-compatible servers in vLLM and SGLang, standard tool calls, a 1M-token context and Meta's own serving docs. Serving the 537 GB NVFP4 checkpoint takes four B300 GPUs, Meta's download is gated by manual review, and the licence adds attribution and a revenue threshold for model resellers.

**OpenAI API.** Official OpenAPI document and an llms.txt index. Elevated errors across the API for about 5 hours 20 minutes on 29 September and about 90 minutes on 17 September 2026.

## Before you call either

### Muse Spark Open

1. Start vLLM or SGLang with `--reasoning-parser muse --tool-call-parser muse` (vLLM also `--enable-auto-tool-choice`), or tool calls come back as raw text
2. Set `reasoning_effort` to `low` or `medium` for short tasks. The default is `xhigh`, reasoning can't be turned off, and other values return an error
3. Stop only on `<|eot|>` and end of text. Stopping on `<|eom|>` cuts off tool calls and final answers
4. Stream long generations and leave `max_tokens` room for reasoning, or `content` can come back empty with `finish_reason` `length`
5. Don't call Meta Model API for this model. Use a self-hosted server or a hosted provider's model string, such as `meta-models/muse-spark-open`

### OpenAI API

1. Build on the Responses API. Astra calls tools only there
2. Use `gpt-6-luna` for routing and extraction and `gpt-6.1-sol` for most work. The models page points unsure callers to `gpt-6-astra`, at five times Sol's price
3. Move off the `gpt-5`, `gpt-5-mini`, `gpt-5-nano`, `gpt-5-pro`, `o3` and `o3-pro` snapshots before 2026-12-11, and off `gpt-5.1`, `gpt-5.3-codex` and `gpt-5.4-nano` before 2027-04-01
4. Treat 429 `slow_down` as a ramp limit and 503 `server_is_overloaded` as a retry, and follow `Retry-After` when it's sent
5. Prompts over 272K tokens cost double on input. Trim before you pay for it

## Questions

### Which is better for AI agents, Muse Spark Open or OpenAI API?

OpenAI API scores 83.3 (A) on agent readiness against Muse Spark Open's 53.4 (D), and leads in 6 of 7 scored categories. Muse Spark Open leads on payments & pricing.

### Do Muse Spark Open and OpenAI API need an API key?

Muse Spark Open needs no key. OpenAI API needs an API key.

### Can an agent call Muse Spark Open and OpenAI API without installing anything?

No hosted endpoint is listed for Muse Spark Open. OpenAI API has a hosted endpoint at https://api.openai.com/v1.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/muse-spark-open-vs-openai-api.json, and with the fewest tokens: https://www.anchorterminal.com/compare/muse-spark-open-vs-openai-api.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "muse-spark-open", "b": "openai-api"}`. From a terminal: `anchor compare muse-spark-open openai-api`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/muse-spark-open.json and https://www.anchorterminal.com/api/v1/tools/openai-api.json

## Other comparisons with Muse Spark Open or OpenAI API

- [Claude API vs Muse Spark Open](https://www.anchorterminal.com/compare/anthropic-api-vs-muse-spark-open.md)
- [Claude API vs OpenAI API](https://www.anchorterminal.com/compare/anthropic-api-vs-openai-api.md)
- [Antseed vs Muse Spark Open](https://www.anchorterminal.com/compare/antseed-vs-muse-spark-open.md)
- [Antseed vs OpenAI API](https://www.anchorterminal.com/compare/antseed-vs-openai-api.md)
- [BlockRun.AI vs Muse Spark Open](https://www.anchorterminal.com/compare/blockrun-ai-vs-muse-spark-open.md)
- [BlockRun.AI vs OpenAI API](https://www.anchorterminal.com/compare/blockrun-ai-vs-openai-api.md)
- [Cloudflare AI Gateway vs Muse Spark Open](https://www.anchorterminal.com/compare/cloudflare-ai-gateway-vs-muse-spark-open.md)
- [Cloudflare AI Gateway vs OpenAI API](https://www.anchorterminal.com/compare/cloudflare-ai-gateway-vs-openai-api.md)
- [Cloudflare Workers AI vs Muse Spark Open](https://www.anchorterminal.com/compare/cloudflare-workers-ai-vs-muse-spark-open.md)
- [Cloudflare Workers AI vs OpenAI API](https://www.anchorterminal.com/compare/cloudflare-workers-ai-vs-openai-api.md)
- [Cohere Chat API (Command models) vs Muse Spark Open](https://www.anchorterminal.com/compare/cohere-chat-vs-muse-spark-open.md)
- [Cohere Chat API (Command models) vs OpenAI API](https://www.anchorterminal.com/compare/cohere-chat-vs-openai-api.md)
- [DeepInfra vs Muse Spark Open](https://www.anchorterminal.com/compare/deepinfra-vs-muse-spark-open.md)
- [DeepInfra vs OpenAI API](https://www.anchorterminal.com/compare/deepinfra-vs-openai-api.md)
- [DeepSeek API vs Muse Spark Open](https://www.anchorterminal.com/compare/deepseek-api-vs-muse-spark-open.md)
- [DeepSeek API vs OpenAI API](https://www.anchorterminal.com/compare/deepseek-api-vs-openai-api.md)
- [Gemini Developer API vs Muse Spark Open](https://www.anchorterminal.com/compare/gemini-api-vs-muse-spark-open.md)
- [Gemini Developer API vs OpenAI API](https://www.anchorterminal.com/compare/gemini-api-vs-openai-api.md)
- [GroqCloud vs Muse Spark Open](https://www.anchorterminal.com/compare/groq-vs-muse-spark-open.md)
- [GroqCloud vs OpenAI API](https://www.anchorterminal.com/compare/groq-vs-openai-api.md)
- [Meta Model API vs Muse Spark Open](https://www.anchorterminal.com/compare/meta-model-api-vs-muse-spark-open.md)
- [Meta Model API vs OpenAI API](https://www.anchorterminal.com/compare/meta-model-api-vs-openai-api.md)
- [Mistral AI API vs Muse Spark Open](https://www.anchorterminal.com/compare/mistral-api-vs-muse-spark-open.md)
- [Mistral AI API vs OpenAI API](https://www.anchorterminal.com/compare/mistral-api-vs-openai-api.md)
- [Muse Spark Open vs Novita AI](https://www.anchorterminal.com/compare/muse-spark-open-vs-novita-ai.md)
- [Muse Spark Open vs OpenRouter](https://www.anchorterminal.com/compare/muse-spark-open-vs-openrouter.md)
- [Muse Spark Open vs Prism Inference](https://www.anchorterminal.com/compare/muse-spark-open-vs-prism-inference.md)
- [Muse Spark Open vs RouterPlus](https://www.anchorterminal.com/compare/muse-spark-open-vs-routerplus.md)
- [Muse Spark Open vs SambaCloud](https://www.anchorterminal.com/compare/muse-spark-open-vs-sambanova.md)
- [Muse Spark Open vs SiliconFlow](https://www.anchorterminal.com/compare/muse-spark-open-vs-siliconflow.md)
- [Muse Spark Open vs StepFun API](https://www.anchorterminal.com/compare/muse-spark-open-vs-stepfun-api.md)
- [Novita AI vs OpenAI API](https://www.anchorterminal.com/compare/novita-ai-vs-openai-api.md)
- [OpenAI API vs OpenRouter](https://www.anchorterminal.com/compare/openai-api-vs-openrouter.md)
- [OpenAI API vs Prism Inference](https://www.anchorterminal.com/compare/openai-api-vs-prism-inference.md)
- [OpenAI API vs RouterPlus](https://www.anchorterminal.com/compare/openai-api-vs-routerplus.md)
- [OpenAI API vs SambaCloud](https://www.anchorterminal.com/compare/openai-api-vs-sambanova.md)
- [OpenAI API vs SiliconFlow](https://www.anchorterminal.com/compare/openai-api-vs-siliconflow.md)
- [OpenAI API vs StepFun API](https://www.anchorterminal.com/compare/openai-api-vs-stepfun-api.md)